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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Posted on 19 January 2012 by John Mason

In December 2011, following a fresh flurry of sometimes conflicting media reports about methane outgassing on the East Siberia Arctic Shelf (ESAS), we decided to go and talk to the people doing the work on the ground. We are pleased to report that Dr Natalia Shakhova (NS below) of the University of Alaska in Fairbanks agreed to be interviewed by the author, on behalf of Skeptical Science, via email. Here are the responses, verbatim, to our questions.

Above: Bathymetric map (source - NOAA) of the Arctic with key features noted and the subject area highlighted in red.

SkS: In your JGR paper from 2010 you state that methane hydrate in Siberia can occur at depths as shallow as 20 m. Have any such remarkably shallow methane hydrate deposits on the ESAS been directly observed/sampled and if so, how could methane hydrate have formed at such depths?

NS: Yes, such shallow hydrates were sampled in Siberia. They form as a result of the so-called “self-preservation phenomenon” and they are termed “metastable”. This phenomenon has been intensively studied by Russian geologists starting in the late 1980s.

SkS: Your 2011 field season is reported to have located kilometre-diameter plumes of outgassing methane. Are these located in areas visited in previous seasons?

NS: These were new sites from that part of the ESAS that was investigated very sparsely before. In our previous investigations we mainly focused on the shallower part of the ESAS, which composes about 70% of the total area and provides a very short conduit for methane to escape to the atmosphere. Besides, because we worked mostly on small vessels, we were not allowed to navigate far enough from the coasts to reach the mid-outer shelf where water is relatively deep on the scale of the shallow ESAS (>50 m depth). That is why deeper waters were under-represented and were considered a minor contributor to annual emissions. Last summer’s findings made us re-consider our previous constraint on the annual emission budget; they highlight the need to further assess underestimated components of annual fluxes from the ESAS.

Searching for methane in such an extensive area is truly like searching for a needle in a haystack. The ESAS is more than 2 million square kilometers in extent. Even if we study ~10 000 km2 every year (100x100 km, which is a lot!), it will take >200 years to investigate the entire ESAS! Even then, the probability of finding a hot spot 1 km in diameter within the study area will still be only 0.01%.

SkS: Have you done any analyses/isotopic studies of the fugitive gas to see if anything can be learned about its provenance (i.e., biogenic, thermogenic, destabilized hydrate or a combination of these)?

NS: Yes, we conducted an isotopic analysis to obtain the isotopic signature of the methane dissolved in the water column. The isotopic signature indicates a mixture of methane of different origins. We are currently making an effort to investigate particular sources.

SkS: Do the observed methane outgassing sites tend to correlate with features seen on acoustic imaging of the sea bed (e.g. taliks, pock marks, fractures) or on deep seismic data (e.g. fault-zones, anticlines and other structures)?

NS: We believe that methane outgassing sites primarily correlate with features like those you list above. Our data, although they are still limited, clearly exhibit such a correlation. Unfortunately, there are some limitations in usage of both hydro-acoustic and deep seismic methods imposed by the shallowness of the water column and the ubiquity of shallow gas fronts in the sediments. In addition, our ability to obtain extensive records was constrained by our limited funds; to date we only have ~3000 nautical miles of such recordings.

SkS: A critical question at this point is whether the outgassing is a recent development as a consequence of the dramatic Arctic warming of the past thirty years, or an ongoing, long-term response to the Holocene inundation of the ESAS. What are your thoughts on this and, on a similar line of enquiry, would it be possible to determine the age of the organic matter the methane was originally derived from?

NS: An entire second paragraph of our paper published in Science (Shakhova et al., 2010) is devoted to addressing this question! We were the ones who hypothesized - and devoted our entire study to testing this hypothesis - that methane release from the Arctic shelf is determined by the change in thermal regime of permafrost inundated thousands of years ago. I do not understand why this question should arise over and over again or, moreover, be considered critical. As we deal with the long-lasting permafrost warming caused by the warming effect of the overlying seawater, is there any logic in negating the contribution of the recent warming, which caused additional warming of that overlaying sea water? I believe that there is absolutely no point in trying to determine who is responsible, Mother Nature or human beings. Whoever is responsible, the consequences will be the same.

As for determining the age of the organic matter the methane was derived from, it is very hard to distinguish between modern and ancient sources. The mean age of organic matter preserved even in the surface sediments in the ESAS is 6-8 thousand years, and when you go deeper, you find older organic matter. “Talik” is a term used to describe an unfrozen layer of ground within a still-frozen permafrost body. As taliks develop within the sub-sea permafrost, organic matter of different ages could provide the substrate for methanogenesis. This means that modern methane could be produced from organic matter of different ages, and this is also true of pre-formed methane.

SkS: The recent reports of substantial releases of methane on the ESAS prompt us to ask how these observed emissions could detectably change global atmospheric methane concentrations and in what timeframe?

NS: To date, we have only taken the very first steps down the long path of learning enough to answer this question. We officially reported only 8 Tg of methane was being released from the ESAS per year. This reported amount is <2% of the total annual global methane release and would not detectably change global atmospheric methane concentrations. However, we did not incorporate a few emission components – probably the most important ones - because of some uncertainties still remaining concerning their constraints. Newly obtained data, without question, indicate that annual methane emissions from the ESAS have been underestimated. To say how significant the underestimated components are, and to identify the mechanisms responsible for such substantial releases, we need to carefully analyze obtained data and, very likely, conduct further investigations on a broader scale. To be able to answer your question, which is a core question of our study as well, we need to establish at least a few observatory sites to trace dynamic atmospheric concentrations of methane; we need to develop a monitoring net to detect changes occurring in known plume areas; we also need to continue all-season observations in this region to study temporal and spatial variability in methane releases and the factors that determine this variability. We undoubtedly need to learn much more than we currently know. We call for the involvement of serious funding organizations to give this study the level of support that is consistent with the importance of this topic.

SkS: With respect to future events, in your EGU 2008 abstract it is stated that "we consider release of up to 50Gt of predicted amount of hydrate storage as highly possible for abrupt release at any time". This represents a colossal quantity of gas. How quickly could such a release occur and what would be the most likely mechanism?

NS: I believe that the non-gradual (massive, abrupt) emission mode exists for a variety of reasons. First, wherever in the World Ocean such methane outgassing releases from decaying hydrates occur, they appear to be torch-like with emission rates that change by orders of magnitude within just a few minutes. Note that there was no additional seal such as permafrost to restrict emissions for hundreds of thousands of years anywhere in the World Ocean. Imagine what quantity of methane has been stored beneath sub-sea permafrost if even now, when the permeability of permafrost is still limited, the amount of methane annually escaping from the ESAS is equal to that escaping from the entire World Ocean. Another important factor is that conversion of hydrates to free gas leads to a significant increase in the gas pressure. This highly-pressurized gas exerts a geological power that creates its own gas migration pathways (so-called “chimneys” within sediments). It is even more important to understand that the nature of the permafrost transition from frozen to unfrozen is such that this physical process is not always gradual: the phase transition itself appears to be a relatively short, abrupt transformation, like opening a valve. Remember that the gas “pipeline” is highly pressurized. There could be several different triggers for massive releases: a seismic or tectonic event, endogenous seismicity caused by sediments subsiding pursuant to hydrate decay, or sediment sliding on the shelf break; the shelf slope is very steep, and the sedimentation rates are among the highest in the ESAS. As for the amount that could possibly be released, this estimate represents only a small fraction of the total amount of methane believed to be stored in the ESAS (3.5% of 1400 Gt). Because these emissions occur from extremely shallow water, methane could reach the atmosphere with almost no alteration; the time scale of such releases would largely depend on the spatial distribution and capacity of the gas migration pathways.

SkS: A previous methane release of such a magnitude, occurring abruptly, would logically manifest as a spike in the global methane concentration record, yet the ice-core methane record has no such spikes during previous interglacials. Is there any evidence for massive methane release events having occurred further back - e.g. at any point during the Cenozoic?

NS: You would better address such a question to a specialist in paleo-climatology. To my knowledge, there are a few episodes in the Earth’s history attributed to abrupt methane releases. Interpretation of ice-core methane records may not be relevant, because these records are too short to reach back to the entire Cenozoic.

Skeptical Science would like to thank Dr Shakhova for her contributions.

Notes

The "self preservation phenomenon" mentioned by Dr Shakhova in her reply to the first question is well-known in Russian and other northern petrochemical industry circles, where much discussion may be found. It is temperature-dependent i.e. it requires fairly low temperatures to work. For more information, see Self-preservation of gas hydrates (PDF) for a briefing.

Summary

The research team have located new and large (~1km wide) plumes of outgassing methane, in areas not previously investigated, so this is not necessarily a recent development: at least, there are no previous data from these areas to compare the large plumes with.

That the area has seen warming over a prolonged time since the Holocene transgression and that there has been an additional, sharp recent warming event is well-documented. Whether there is increased outgassing caused by the additional recent warming is an important question that requires urgent investigation, a point indeed made in Shakhova et al's 2010 paper in Science - PDF - see last paragraph.

Further work will better constrain known current methane emissions to the atmosphere, currently estimated to be 8 Tg (1 Tg=1 million tonnes) per year. Clearly, because new sources have been identified, the figure is greater than 8Tg but how much so remains to be discovered.

A large (multi-gigaton) abrupt release event is considered possible, but when is not known. It is important to remember that hydrocarbons, including methane, migrate upwards through the Earth's crust from their source-rocks due to their low density. Basic oil geology tells us that recoverable oil and gas deposits occur where such upward migration has been blocked by an impermeable barrier (an oil- or gas-trap) such as a salt-dome or anticline including thick impermeable strata such as a clay-bed. In such places, the accumulation can build up to the point where the oil/gas is in an highly pressurised state - hence the "blowouts" that have been recorded over the years in some oilfields. What Shakhova is suggesting is that if buried gas hydrates destabilise, what could result is accumulations of pressurised methane capped off by permafrost, which because it is degrading might lose its effectiveness as a gas-trap. The same point would, I suggest, apply to non-hydrate derived methane i.e. gas that has remained as gas. What one would likely see in such a scenario would be a strong increase in outgassing, not in one great "burp" at one locality but via multiple pathways up through the defrosted sediment over a wide area.

David Archer, who has worked extensively with gas hydrates, looks at some release scenarios over at Realclimate, here and here.

Some afterthoughts

In February 2002, the then U.S. defence secretary Donald Rumsfeld famously said: "There are known knowns; there are things we know we know. We also know there are known unknowns; that is to say we know there are some things we do not know. But there are also unknown unknowns – there are things we do not know we don't know." He was lambasted and ridiculed for this at the time. However, at face value, all politics aside, the statement has more than a ring of truth to it.

My scientific background is in mineralogy, and I hope I may offer an analogy which illustrates what is meant by "known knowns, known unknowns and unknown unknowns". During the 1980s, I and a number of other mineralogists started to turn up samples of a mineral forming beautiful vivid pale-green spiky crystals. These were found at old metal-mines in Mid-Wales and the English Lake District: first at one locality then another and another. Despite having all the tools of mineral identification at our disposal, including x-ray diffraction and the electron microscope, we could not match it to any known species. Before we started to find specimens, it had lain there in the mine spoil, an unknown unknown, for centuries. Now we had specimens and could study it but not identify it, it was a known unknown. Finally, nearly twenty years after the first discovery, it became a known known - redgillite, named after one of its localities: a basic sulphate of copper with its crystallography and chemistry described in detail in the peer-reviewed journal Mineralogical Magazine.

above: from unknown unknown to known unknown to known known: redgillite, first described in 2004.

I offer this not as an off-topic distraction but as an example of the way in which science proceeds. In almost every case it is the same: only the timescale may vary. Something new is discovered yet is not fully understood. That uncertainty, however, gives pointers towards follow-up work: in time the uncertainties are whittled away one by one and the whole picture becomes clear. It is a journey which will be familiar to anyone working in any of the many branches of academic research. Shakhova and her colleagues have embarked on a journey of challenging proportions: less than a decade ago they discovered what had to that point been an unknown unknown. Now they have described some of the known knowns: we now know without doubt that methane is venting to Earth's atmosphere from parts of the ESAS seabed in copious quantities as a response - a positive feedback - to warming. Furthermore, they have identified many of the known unknowns for follow-up study. They have rightly called for the setting-up of an observational network in the area and they are planning their research for the coming years in a physically and logistically-challenging area.

Outside of science, people seem to work differently a lot of the time, wanting a black-or-white world where everything is a known known. That there are no absolute, cover-all conclusions yet from the ESAS might come as a disappointment to some. However, this is maybe a time to reflect that, 116 years ago, Arrhenius figured out that adding carbon dioxide to the Earth's atmosphere would raise Earth's surface temperature over time. That has been a known known ever since, reinforced by study after study after study, during which time we have raised carbon dioxide levels well beyond anything during the geologically recent glacial-interglacial cycles, so that we are now heading, decade by decade, towards the climate of the mid-Cenozoic, methane or no methane.

Excellent summary, especially the appropriately cautious tone. I think it's critical that people not give in to either of the obvious temptations regarding Arctic methane hydrates and leap to the conclusion that "we're already screwed beyond hope" or that "it's a tiny contribution to atmospheric methane, wake me up when measured levels jump". The problem, of course, is that the stakes are so enormous that waiting for "hard evidence" in the form of atmospheric levels taking off would squander even more time that we can't spare.

Another question about what's going up in the Arctic relates to the emission rates over the next few years to decades. For the sake of argument, say that the total methane emissions right now turns out to be about double the conservative estimate, and is roughly 4% of worldwide emissions. If this stays constant it's certainly not a welcome addition to our situation, but it's not a bad 1970s disaster movies, either. If, however, continued warming makes that emissions rate climb by half a percentage point a year (e.g. in four years it's up to 6% of worldwide emissions), then we could conceivably be in a world of trouble -- depending on the total amount of methane that would be liberated at that rate.

I really wish that one of the environmentally aware billionaires would fund a huge Arctic monitoring effort, looking for emissions from hydrates as well as permafrost. Better yet would be a cooperative project pooling the resources of a dozen or more countries, but in the current political environment I don't see that happening.

It occurs to me, though IANACS, that a good place to look for potential ESAS methane spikes would be during a long interglacial - MIS-11, for example, lasted ~30k years? - on the basis that the permafrost capping any methane would have a chance to degrade. Are there signs of spikes in the ice cores, or is the time scale too short to be captured (because CH4 has a short atmospheric lifetime)?

It's an excellent interview. The only unfortunate part is Shakova's response on the question of humans sparking the event versus a natural world process. It's the difference between fatal acceptance and necessary response.

The links show how quickly this subject becomes complex, and there is a very real need to make at least a swag on whether this is the start of a very very ugly arctic outgassing eruption.

The most important paper on climate change in quite a while was published two days ago in Science (Shindell et al, 2012: read about it here).

Archer’s thinking makes sense, if you’re not planning on doing anything about the climate. The more you are, the more his downgrading of leaking methane to ‘Nothing’ by taking an absurdly long view becomes quite weird. Huffington Post Oh and will at it, click my user link i wrote an extensive piece about RealClimate as well! Bottom line, the house is burning, when do we start with fighting it?

The methane build up is probably even large than when previous outburst occurred.
The sun is about 30% warmer than it was since a long time ago.
Human induced warming is unprecedented in the long pass.
Sesmic activities increases with warming.

All these thing point to a higher probably that we may see an abrupt emission event.

[DB] Note: All graphics must include accompanying text which provides the context for why the graphic is relevant and germane to the htread on which it is posted. Future graphics-only or link-only will be deleted. FYI.

It would be instructive to compare the Dec 2010 & 2011 graphs with those for a few of the preceding years. In 2009 and 2010 the pressure-patterns over the Arctic were rather unusual - these leading to the very cold wintry weather over NW Europe. In 2011-12, a "normal" polar-vortex pattern has dominated matters. It would, therefore, be interesting to see if December 2009 has any similarity to December 2010 and whether December 2006, 2007 and 2008 are more like December 2011. My line of questioning is based upon whether a trans-polar airflow giving deep Northerly outbreaks across NW Europe better flushes the methane out of the Arctic than the "normal" circumpolar flow.

If you are going to post images, then please could you resize them to 500 pixels? The ones above are huge and they are generating server error messages at times (the 425 alert, if anybody wonders what that is), even with the size-settings you have applied. I have asked the moderators if they can replace them with copies I have resized and saved.

..after 2007 new growing source(s) caused a new growth of CH4. The nature of these sources is a matter of debates.

The current rate of CH4 increase (~ 20 Tg per year for the global troposphere) seems to be constant between 2007 and September, 2011. This increase does not look catastrophic: in early 1980 methane was increasing with a rate 40-50 Tg/year and the rate decreased to zero by 2000. A permanent monitoring is necessary to detect a potential large surge as promptly as possible.

The external links coupled with the ESAS findings suggest an initial reaction of 'new development'.

When global methane concentrations started rising again the fingerprint was increases in both northern and southern hemispheres at the same time. Somehow, the two-year mixing lag across the equator was bypassed - or it was a global phenom. Now hotspots are observed in the ESAS and in the Antarctic. The negative-hypothesis presented in the American WX link at the bottom of the Expert Discussion article is wanting on all counts.

It isn't conclusive, but any dismissive about it isn't because it shouldn't, or the model didn't show it, or the IPCC didn't write it ... they're selling, not telling.

With all due respect to Owl905 @7 I couldn't agree more with Dr Natalia Shakhova's words:

"I believe that there is absolutely no point in trying to determine who is responsible, Mother Nature or human beings. Whoever is responsible, the consequences will be the same."

As I have said before: You don't refuse steer round an iceberg because it is not anthropogenic in origin. If you stand back from the issue, it is possible to see the way arguing about whether global warming is caused by human activities or not is being cleverly used as a reason not to act.

Is global warming happening? - Yes
Is the final amount of warming known? - No
Is it potentially dangerous? – Yes, very
Are greenhouse gasses responsible to some extent - Yes
Do we produce greenhouse gasses? - Yes
Would it help if we reduced our production of them? - Yes
Why don't we act to reduce them? - We are too busy arguing about who has produced those already in the atmosphere.

If Douglas Adams were still alive, I am sure he could write a whole chapter of the HitchHikers Guide to the Galaxy on how the Golgafrinchans tackled climate change based on our efforts on the matter. I know it is off topic, but surely the world’s financial problems would be cured at a stroke if we all adopted the leaf as a unit of currency the way the Golgafrinchans did.

"Is global warming happening? - Yes
Is the final amount of warming known? - No
Is it potentially dangerous? – Yes, very
Are greenhouse gasses responsible to some extent - Yes
Do we produce greenhouse gasses? - Yes
Would it help if we reduced our production of them? - Yes
Why don't we act to reduce them? - We are too busy arguing about who has produced those already in the atmosphere."

Ver. 2

Is global warming happening? - Yes, its been happening since the Little Ice Age, long before manmade greenhouse gases had any chance of affecting temperature rises.

Is the final amount of warming known? - No. We don't even know when the earth is going to start cooling again, as it evidently has time and time again.

Will warming eventually lead to cooling? - Yes, if you believe paleontologists, ice core data, etc..

Aren't both warming and cooling potentially dangerous? – Yes, very, but cooling is much more devastating - think mile of ice over much of North America. How many species would be at risk?

Are greenhouse gasses responsible to some extent - Yes, but we're not sure if the temperature effect of manmade greenhouse gases is significant. The question of the amount of effect of AGW is still hotly debated, as evidenced by the wide range of projected temperatures by the UN IPCC models, and real world observations.

Do we produce greenhouse gasses? - Yes, but not as much as Mother Nature. Water vapour is by far the most abundant GG.

Would it help if we reduced our production of them? - Possibly, but even if every country in the world adopted Kyoto Protocol standards, experts say temperature rise by 2100 would only be delayed by 5 years.

Why don't we act to reduce them? - Financially it does not make sense because proposed reductions wouldn't make a dent in projected temperature rises anyways, except perhaps for worse case computer modelling which currently is not being supported by observations.

If Kurt Vonnegut were still alive, I am sure he could write a whole book on how the 21st Earthlings thought they were saving the planet by reducing CO2, when in fact they were condemning it to an earlier frozen grave in the 22nd Century.

That's the nature of science fiction and non-fiction. When it comes to predictions, science fiction can predict accurately into the next century, while non-fiction can't accurately predict what's happening next week.

If your post survives moderation for being so egregiously off-topic and little more than a "who's who" romp through long-refuted hogwash, then IMO you need to substantiate every single claim you have made with references to peer-reviewed literature or concede that your claims are without merit.

00

Response:

[DB] Yes, saltspringson's comment was a nice example of a Gish Gallop. As such, should he/she feel up to the challenge of actually mounting a defense, the onus will be on he/she to mount said defense of each claim individually, on the most appropriate threads.

"Why don't we act to reduce them[greenhouse gases]? - Financially it does not make sense because proposed reductions wouldn't make a dent in projected temperature rises anyways, except perhaps for worse case computer modelling which currently is not being supported by observations."

Please, saltspringson, get a grip on reality. In this case, that reality is that any reduction we make in our emissions of greenhouse gases will in fact make a dent in actual temperature rises, even if only a small one. Is it really so hard for you to grasp this basic fact?

Let me provide an analogy: You have a bank account that earns interest, and thus the more money you put into the account the more interest you earn. If you stop putting money into the account, or reduce the amount per week you put in, you will reduce the amount of interest you earn. The basic reality of putting man-made greenhouse gases into the environment is that the more we put in, the more warming [interest] will happen.

And please, please, please, never again post with that silly closing line.

Gentlemen, I would appreciate your comments on a PowerPoint I put together of a composite of images of the Arctic from a satellite with microwave sensors (as I understand it), taken in January. Please contact me at my blog for the actual ppt file. The crocodoc thing is not as easy to look at:

To make a point: The latest AIRS methane imaging suggest that not only the ESAS is a major source for methane uptake.

And another uptake is observed recently..

Before 2007, CH4 mixing ratio was nearly stable. The average mixing ratio during the last 6 years over major northern hemispheric countries is similar. However, there has been a significant increase in tropospheric CH4 concentrations after 2007 in most northern hemispheric areas, with slightly larger increases over China.EurekAlert

Please note that unlike other sites, this is not the wild west. You do not get to come in, guns blazing, then twirl your six-shooters and drop them into your holsters while grinning manically.

More to the point:

1) If you have something to say, say it in an appropriate thread. Every comment you have here will be deleted for being off-topic. That's not to say that you can't try to make a point (although honestly, looking through your words, I don't see a single meaningful point in there). But you have to make it on a thread with a relevant topic.

2) You must support what you say with citations. You cannot make an assertion without supporting evidence (e.g. "Will warming eventually lead to cooling? - Yes", "but we're not sure if the temperature effect of manmade greenhouse gases is significant" , "Do we produce greenhouse gasses? - Yes, but not as much as Mother Nature", etc. etc.)

3) We discuss science, not opinions, conjecture, or pseudoscience. As such, it would be best if you raised one point in a comment, not a herd of them, so that it can be discussed and debated rationally.

Oh, and you might want to read the Comments Policy. You've already violated it by being and staying far off topic.

00

Moderator Response: [Rob P] - saltspringson's off-topic comments have been deleted. I have left this post here so that he will hopefully read and absorb the advice it contains, and post any additional comments on the appropriate thread.

saltspringson... "Is global warming happening? - Yes, its been happening since the Little Ice Age, long before manmade greenhouse gases had any chance of affecting temperature rises."

Mmmm... Not so quick there cowboy. That would clearly depend on which temperature reconstruction you were looking at. You're treading in with assumptions where there happen to be significant uncertainties.

John, I left this comment over at the ClimateProgress reposting of the interview, but in case you miss it there:

In your second to last paragraph you say:

"we now know without doubt that methane is venting to Earth's atmosphere from parts of the ESAS seabed in copious quantities as a response - a positive feedback - to warming."

What I would like to know is what in this interview or in other things you have read, seen or heard leads you to come to such a firm conclusion that this is already certainly part of a feedback. I think it most likely is, but this seems to be exactly the thing that is being hotly debated, and I have not seen Shakhova come out and say that it the methane releases she has observed are definitely part of a GW feedback--quite the opposite: she has pointed out that they have NOT made such a claim.

So if you have some source or data that you are basing this conclusion on, I would definitely like to know what it is.

Thanks ahead of time.

Oh, and what do you think of the AIRS images posted above. Art they further evidence that something unusual is going on with Arctic methane this year? Should we expect levels to be much higher already?

In response to your first question, clearly the methane is being released as a feedback to warming. What I was careful NOT to say was to which bit of the warming: that resultant from the Holocene transgression or that heaped upon it by Mankind. At the moment, we don't know, as Shakhove herself says: the point is we need to evaluate the situation further.

How one goes about determining whether the post-1980s abrupt seawater warming reported by Dmintrenko et al is causing this effect I don't know, but I would hazard a guess that should the rate of methane emissions in the coming years be found to be increasing in tune with this extra warming then we should have a pretty good idea, likewise with the ARS data you refer to.

Thanks for the clarification, John. I get the sense that by the time we have a really good idea of what is going on, our goose will already be pretty well cooked.

I wonder if you could clarify something else. If there was a major one-time eruption of methane, of the sort Shakhova discussed (~50 Gt iirc), how long would it take a land-based monitoring station a thousand or so miles away to detect it?

The goose has been in the oven for sometime already! Hence my parting statement, which I think you will tend to find in most articles on this subject.

WRT your question: lots of possibilities to read into this statement still. 50 Gt over what time period? A year? Ten years? Ten hours? Is there enough methane present for it all to come out in one place or, as I suspect, and alluded to in the article, is not a more likely scenario one in which an increase in outgassing via multiple pathways occurs over an extensive area? We don't know.

Detection would depend on synoptic patterns at the time, which would control boundary-layer windfields in terms of direction, fetch and speed. An alternative might occur if a 5-15% methane-air mix was generated: enough of that and any ignition-source would provide something more likely to be picked-up on seismographs.... However, one could speculate until the cows come home and such topics are likely better for discussion over a pint or two of beer!

Other questions likewise abound: thus I'm looking forward to examining the next data-release and in due course the results from further fieldwork. I am sure we will be returning to this topic again and again in the coming years. But for now, I would caution that is very tempting to jump to conclusions WRT Arctic methane, but in doing so without strong evidence, one is diverging from science, which is something I'd prefer to leave to politicians!

The lack of a methane spike in ice cores might not be all that mysterious. Methane in the atmosphere has a half life of around 7 years due to its combination with oxygen. Even if there is a huge outgassing of methane, a bubble of air trapped in ice is mostly Oxygen with a little methane. In addition, the top 50 to 100 m of a forming ice sheet is still connected to the atmosphere by diffusion which will provide more oxygen and blur the sharpness of any sudden production of carbon rich gas. A huge outpouring of methane should show up in ice cores as a Carbon dioxide spike as is seen at the beginning of each interglacial.
http://mtkass.blogspot.com/2011/08/end-of-ice-ages.html

Interesting ideas, William. Am accumulating literature on this whole problem, which deserves more exploration I think. However, a rapid methane release in the order of many tens of Gt would show up starkly as a much-bigger-than-usual CO2-spike, compared to those you cite. From what I am reading, though, smaller events may actually be quite common, as a response to falling sea-levels, and ironically then trigger deglaciation. Need to read up much more on this, though.

The age of the methane is of interest. If it is found to be greater than the 50,000 years that can be measured with carbon dating, this would point to a geological source such as outgassing from coal, shale or liquid hydrocarbon deposits. This would reinforce the idea that such seeps would be trapped under ice sheets as clathrates once the ice sheet had reached about 300m deep. Over the roughly 100,000 years that glacials last, a lot of methane can accumulated only to be released when a milankovitch nudge starts the melt.

It could be that no methane pulse would be seen in ice bubbles from Antactic or Greenland cores. The half life of methane is about 7 years and much of the oxidation is due to hydroxyl ions in the upper atmosphere. Whether this oxidation would continue inside the ice is a moot point. However, the top 70 or so meters of a forming ice sheet still exchanges gas from the atmosphere. The bubbles are not yet closed. This would tend to blur or even eliminate a methane signature in ice bubbles even if it did occur in the atmosphere.

Another unsettling effect of methane release, especially on the continental shelf is the loosening of the sediment both by the melting of the "clathrate permafrost" and the expansion of the gas, turning the sediment into a fluidized bed. Sudden slumps on continental shelves have been implicated in localized but very severe tsunamis. Will the coastal people of the Arctic ocean experience some of these in the not too distant future.

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